diff --git a/ide/project.pp b/ide/project.pp
index 0a893f0ca0..c2a4c7d641 100644
--- a/ide/project.pp
+++ b/ide/project.pp
@@ -4260,6 +4260,7 @@ procedure TProject.SetSessionStorage(const AValue: TProjectSessionStorage);
 begin
   if SessionStorage=AValue then exit;
   inherited SetSessionStorage(AValue);
+  Modified:=true;
   UpdateSessionFilename;
 end;